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In order to evaluate safety assessment of the Sanctuary of Vicoforte, Italy, a series of non-destructive tests were carried out for diagnostic inspection of its deterioration. Delamination of stone finishing and fresco painting were detected. Dynamic ambient vibration test was carried out and the relevant modes of vibration were identified resorting to the stochastic subspace identification method. The first two natural frequencies of the Sanctuary of Vicoforte were estimated to be about 1.93 Hz and 2.07 Hz in East-West and North-South directions, respectively. Therefore, the dome seems to be vulnerable to severe earthquakes characteristic of the local seismicity such as we experienced in recent years.

Terahertz and sub-terahertz waves are unexplored waves range between infrared waves and microwaves. This range features with unique characteristics of both light straightness and electromagnetic wave transmission. Terahertz and sub-terahertz waves are attractively new diagnose method of inner objects because they are safer compared to normal non-destructive inspection methods involving high energy, such as X-rays. Hereby, a novel non-destructive inspection method for concrete and reinforced concrete structures is proposed using sub-terahertz reflection imaging. In Japan, where earthquakes and other natural disasters frequently occur, this technique is expected to be used to remotely inspect the deterioration of damaged RC structures that are difficult to access to. The results of this study confirm that various types of condition changes in concrete can be found by using this sub-terahertz imaging method. The presence of cracks/voids in concrete and under the finishing layers was successfully detected based on differences in reflectance. Moreover, the presence of metals inside/behind the concrete specimens was able to be identified. It was also confirmed that the decline rate of the mechanical properties of concrete could be evaluated according to the decrease in reflectance due to the existence of fine cracks.

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